EP0784413B1 - N x N wavelength router and associated optical routing method and communication network - Google Patents

Description

The present invention relates to a router N x N of length wave, as well as an associated routing method, more particularly for a communications network.

Significant developments in teletransmission by channel optics connect each user to a transmission center or relay via fiber optic transmission fitted with an optical component at each of their ends intended to connect the modulated light emitter to the fiber to make penetrate the light, or at the other end, to collect the light to direct it towards a detector which will decode the optical signal for transform it into an electrical or electronic signal usable in a usual receiver.

The telecommunications networks thus obtained make necessary the realization of commutations in great number by the through complex devices of the optical switch type.

To achieve such an optical switch, we have developed specific components for N inputs and N outputs, able to connect any input to any output by wavelength adjustment. This component, called router N x N wavelength or WDM (Wavelength Division Multiplexer), usually has N connected diffracting input elements respectively at the inputs and N diffracting output elements arranged opposite the input diffracting elements and connected respectively at the outputs. Each of the diffracting elements input is able to produce for a given signal transmitted to a wavelength, an image arranged in a focal plane corresponding to any of the diffracting output elements. The selection of the output element is subject to the length signal wave.

At each input fiber-output fiber pair, is therefore associated transmission wavelength. The global spectrum of transmission of the entire router N x N is thus presented under the shape of a comb with teeth located at these wavelengths. For identical diffracting elements arranged at intervals equal in an input line and an output line, 2N-1 lengths separate waveforms are used in the transmission spectrum.

One drawback of these traditional routers is their size and complexity, 2N diffracting elements being required.

In addition, the wavelength ranges between the teeth are lost areas. Since the tape spectral usability is limited, this results in a limitation of the number of transmission wavelengths. The possible number users is thus considerably restricted. For exemple, for a total spectral band limited to 30 nm, and the spacing between two transmission wavelengths being 1 nm, the number of transmission wavelengths cannot exceed 30, which restricts the number of users to fifteen.

On the other hand, the teeth of the transmission spectrum have a width at half height or FWHM (Full Width Half-Maximum) usually small compared to length spacing transmission wave, which makes it difficult to select a emission wavelength, because positioning in a spectrum tooth requires high precision.

To decrease the lost areas and increase the useful area by wavelengths, one way is to bring the core closer to fibers. The ratio R of the width at half height of the teeth on their spacing indeed increases with the ratio of the diameter of the heart fibers over their distance. Thus, can the ratio R reach a value of 0.4 when fibers with hearts of diameter 10 µm are spaced successively by 22 µm.

However, such fiber reconciliations are found technically limited, and lead moreover to a phenomenon of diaphotia, the light passing directly from a fiber core to a another neighbor.

In order to increase the capacities of the routers, it has been proposed to associate several elementary routers. In devices existing routers are connected as input to couplers achromatic through multiplexing units and temporal demultiplexing. The inputs of each of the couplers can thus be linked to the inputs of each of the routers by means of an interconnection network. The capacity of the router thus obtained is significantly increased compared to that of basic routers, the total number of users being the sum of users planned for the different basic routers.

However, such a network produces significant losses. Moreover, it involves the implementation of complex processes in order to carry out the time multiplexing. Furthermore, the problem previously mentioned wavelength selections remain present.

The SHARONY document: "Broadcast and Switch" - "A new class of WDM networks for high switching-speed, high connectivity applications ”, PHOTONICS IN SWITCHING, vol. March 16, 15, 1993, PALM SPRINGS US, pages 196-198, discloses an optical router with two floors including the “Wavelength Selective Switches” on the second stage receive multiplexed optical signals from each of the star couplers on the first stage.

The present invention relates to an N x N wavelength router valid for a large number of users, implying low losses and simple to carry out and to implement.

The present invention also aims at such an N x N router. avoiding any problem of crosstalk, and having a width to half height ratio on spacing between high transmission wavelengths.

The present invention is also directed towards a method of optical routing easy to implement and avoiding interference between signals.

The invention also aims at a communications network based on optical means, valid for a large number user-friendly, reliable, involving low energy losses, and simple to make and use.

To this end, the invention relates to a router N x N of length waveform with N inputs and N outputs, intended to transmit optical signals each having a wavelength, inputs to the exits. The N x N router also includes means switch capable of routing each of the optical signals of one any of the N inputs to any of the N outputs in function of the signal wavelength.

• n coupleurs m x m ayant chacun m entrées et m sorties, N étant égal à n X m et les N entrées des n coupleurs m x m étant les entrées du routeur N x N,
• m routeurs n x n ayant chacun n entrées et n sorties, chacune des n entrées étant reliée à une des sorties de, respectivement les n coupleurs m x m et les N sorties des m routeurs n x n étant les sorties du routeur N x N. Chacun des routeurs n x n est apte à aiguiller un signal optique ayant une longueur d'onde, de l'une quelconque de ses n entrées vers l'une quelconque de ses n sorties, en fonction de la longueur d'onde du signal, le routeur n x n ayant un spectre de transmission en fonction de la longueur d'onde sous forme d'un peigne.

The referral means include:

• n mxm couplers each having m inputs and m outputs, N being equal to n X m and the N inputs of the n mxm couplers being the inputs of the router N x N,
• m nxn routers each having n inputs and n outputs, each of the n inputs being connected to one of the outputs of, respectively the n mxm couplers and the N outputs of the m routers nxn being the outputs of the router N x N. Each of the routers nxn is able to route an optical signal having a wavelength, from any of its n inputs to any of its n outputs, depending on the wavelength of the signal, the router nxn having a spectrum of transmission as a function of the wavelength in the form of a comb.

According to the invention, the combs of the m routers n x n are different from each other, so as to make selection possible wavelength function for any of the N inputs of the router N x N, one of the m routers n x n and one of the n outputs of this router n x n.

The transmission spectrum of an optical router is called the spectral distribution of the light flux at its outputs, produced by a luminous flux of spectrum extended over the entire band of operation of the router applied to all of its inputs.

The router according to the invention implements different spectra according to the different routers n x n making it possible to select the wavelength, for a given input, of the router n x n concerned and within it, the intended exit route. This device therefore no time multiplexing required and allows upstream use n x n routers, a simple assembly of channel switches such as that claims.

As a whole, the router N X N can admit a spectrum of transmission in the form of a comb with very close teeth. For a given range of usable wavelengths, the number N input and output can be significantly increased, without risk of crosstalk and without any particular technical problem.

In addition, the ratio R for the overall transmission spectrum can be greatly increased. The relative widening of the width of teeth therefore allows a selection of emission wavelengths less strict than in existing devices.

The greater the number of router n x n, the more the teeth of this spectrum can be brought together, but at the cost of increased complexity of the assembly.

Preferably, the transmission spectrum of each of the m routers n x n includes wavelength bands and each of these bands comprising teeth, the transmission spectra of m n x n routers have their bands interspersed.

This configuration makes it possible to obtain a spectrum of transmission with complementary bands from different n x n routers. This can be particularly advantageous when transmission wavelengths are grouped by packets in each of the n x n routers.

In an advantageous embodiment of this configuration, the combs of the m x n routers have their teeth inserted.

In this case, the teeth of the overall transmission spectrum alternatively come from a separate n x n router, which allows to obtain with respect to each of the routers n x n taken in isolation, a the closer the teeth, the greater the number of routers n x n is large. The ratio R can thus be multiplied by m.

In an advantageous embodiment, the comb of each of m routers n x n has teeth completely dissociated from the teeth other combs.

The teeth of the global transmission spectrum can thus be clearly distinguished from each other, while being close. of the overlapping teeth from different spectra of routers n x n are however also possible.

According to a first embodiment of the router N X N, each couplers m x m is an achromatic coupler with distribution uniform energy between its outputs.

Inexpensive and customary elements are used in this way.

According to a second embodiment, each of the couplers m x m is a wavelength distribution coupler capable of transmitting energy of an optical signal having a wavelength, only by the output of the coupler m x m connected to the router n x n whose comb understands this wavelength.

This second embodiment is advantageous in that it avoids any loss of energy due to the m x m couplers, by channeling the signals upstream from the routers n x n as a function of the length waveform of the optical signal.

In a preferred embodiment of the N x N router, the m x m couplers are composed of 2 x 2 couplers each having two inputs and two outputs.

Such 2 x 2 couplers, also known as X couplers, are elements commonly available and easily usable in association.

In this preferred embodiment, the router N x N advantageously includes a first level of 2 x 2 couplers whose inputs are the inputs of the router N x N, and a last level of 2 x 2 couplers whose outputs are connected to the inputs n x n routers. The inputs of the 2 x 2 couplers which do not belong to the first level, are connected to outputs of 2 x 2 couplers, and the outputs of the 2 x 2 couplers which do not belong not at the last level, are connected to 2 x 2 coupler inputs.

It is interesting that the N x N router has couplers with Y each having a main arm and two secondary arms, the inputs and outputs of the router N x N being connected to the arms main couplers in Y. The router N x N allows to send optical signals simultaneously from its inputs to its outputs and from its outputs to its inputs, the optical signals flowing in opposite directions in the two secondary arms of each of Y couplers.

This last device allows to gain a factor 2 in the number of inputs and outputs available, because the same length wave allows communications in one direction and in the other router N x N. The claimed characteristic therefore contributes to increase the number of users of a transmission system, simple way.

• un support de transmission comprenant une première rangée des n entrées et une seconde rangée des n sorties, les première et seconde rangées étant disposées parallèlement et le support de transmission ayant une surface de transmission plane,
• un élément diffractant disposé en regard de la surface de transmission,
• une optique de focalisation placée entre le support de transmission et l'élément diffractant,

l'élément diffractant et l'optique de focalisation étant aptes à produire de l'une quelconque des entrées une image correspondant à l'une quelconque des sorties, en fonction de la longueur d'onde des signaux optiques.Preferably, each of the nxn routers comprises:

• a transmission medium comprising a first row of the n inputs and a second row of the n outputs, the first and second rows being arranged in parallel and the transmission medium having a planar transmission surface,
• a diffracting element placed opposite the transmission surface,
• focusing optics placed between the transmission support and the diffracting element,

the diffracting element and the focusing optics being capable of producing from any of the inputs an image corresponding to any of the outputs, as a function of the wavelength of the optical signals.

This configuration of n x n routers is both compact and economic.

The invention also relates to an optical routing method implemented by means of an N × N router according to the invention. In this process, we send optical signals each having a wavelength, from the inputs of the N x N router to its outputs.

The method according to the invention is characterized in that for ability to simultaneously send optical signals of at least two of the m inputs of at least one of the n couplers m x m, in direction of the same one of the N outputs of the router N x N without risk of interference, optical signals have different wavelengths each other.

Thus, the coupling of the input signals in the coupler m x m concerned does not prevent a discernment of these output signals from router N x N.

According to a first preferred embodiment of this method, the output of the router N x N being one of the n outputs of one of the m routers n x n and the comb of the router n x n having teeth, the wavelengths of the optical signals are distributed in one of the teeth.

According to a second preferred embodiment of this process the wavelengths of the optical signals have orders distinct.

The invention also relates to a communications network. comprising at least one N x N router having any one of the preceding characteristics, or more of them in association, or implementing any of previous features of the routing process.

• les Figures 1A et 1B sont des représentations schématiques d'un routeur 4 x 4 de longueur d'onde utilisé dans un routeur N x N selon l'invention, la Figure 1A montrant une vue d'ensemble du routeur 4 x 4 et la Figure 1B, une vue de face de son plan de fibres ;
• la Figure 2 représente un routeur 8 x 8 de longueur d'onde selon l'invention, comportant quatre coupleurs 2 x 2 et deux routeurs 4 x 4 tels que celui schématisés sur les Figures 1A et 1B ;
• la Figure 3 montre les spectres de transmission respectifs des deux routeurs 4 x 4 du routeur 8 x 8 de la Figure 2 ;
• la Figure 4 est une représentation schématique d'un routeur 12 x 12 de longueur d'onde selon l'invention, comportant trois coupleurs 4 x 4 et quatre routeurs 3 x 3, et à double sens de transmission ;
• la Figure 5 est une vue détaillée d'un des coupleurs 4 x 4 du routeur 12 x 12 de la Figure 4 ;
• la Figure 6 montre les spectres de transmission respectifs des quatre routeurs 3 x 3 du routeur 12 x 12 de la Figure 4 ;
• la Figure 7 montre les spectres de transmission respectifs des deux routeurs 4 x 4 du routeur 8 x 8 de la Figure 2, et représente les longueurs d'onde des signaux transmis dans un mode préféré de mise en oeuvre du procédé de routage ;
• la Figure 8 montre dans un mode de mise en oeuvre la matrice de longueur d'onde 20 X 20 d'un routeur 20 x 20.

The invention will be better understood by referring to particular applications given by way of examples and represented by the appended drawings:

• Figures 1A and 1B are schematic representations of a 4 x 4 wavelength router used in an N x N router according to the invention, Figure 1A showing an overview of the 4 x 4 router and Figure 1B, a front view of its plane of fibers;
• Figure 2 shows an 8 x 8 wavelength router according to the invention, comprising four 2 x 2 couplers and two 4 x 4 routers such as the one shown in Figures 1A and 1B;
• Figure 3 shows the respective transmission spectra of the two 4 x 4 routers of the 8 x 8 router of Figure 2;
• Figure 4 is a schematic representation of a 12 x 12 wavelength router according to the invention, comprising three 4 x 4 couplers and four 3 x 3 routers, and with two directions of transmission;
• Figure 5 is a detailed view of one of the 4 x 4 couplers of the 12 x 12 router of Figure 4;
• Figure 6 shows the respective transmission spectra of the four 3 x 3 routers of the 12 x 12 router of Figure 4;
• Figure 7 shows the respective transmission spectra of the two 4 x 4 routers of the 8 x 8 router of Figure 2, and shows the wavelengths of the signals transmitted in a preferred embodiment of the routing method;
• Figure 8 shows in a mode of implementation the 20 X 20 wavelength matrix of a 20 x 20 router.

A basic 4 x 4 router, used in an N x N router according to the invention, comprises a diffraction grating 50 disposed opposite of a plan 62 of fibers, as can be seen in FIG. 1A. The 4 x 4 router also includes focusing optics such as than a lens 59. Input fibers 51, 52, 53, 54 lead to the plan 62 of fibers being arranged in line, as well as output fibers 55, 56, 57, 58, the plane 62 of fibers being shown from the front in Figure 1B. Input fibers 51-54 are arranged parallel to the output fibers 55-58 and facing each other in the plan 62. The network 50 is capable of producing any input fibers 51-54 an image arranged in a focal plane which matches any of the output fibers 55-58 function of The wavelength. An incident ray 60 containing information transmitted by one of the input fibers from a user transmitter is thus transformed into a returned ray 61 by means of the lens 59 and the network 50 which is directed towards a receiving user through one of the output fibers. Depending on the wavelength of the signal emitted, any of the four sending users can communicate with any of the four receiving users.

The relationships giving the wavelengths which make it possible to pass from any of the input fibers to any of the output fibers can be shown diagrammatically in a 4 × 4 matrix of the type shown below. The rows correspond to the input fibers 51-54 and the columns to the output fibers 55-58. All communications through the 4 x 4 router require 7 wavelengths λ _i , i varying from 1 to 7, classified in ascending order.

The realization of a basic nxn router, similar to that described, with any n, can be carried out as for the 4 x 4 router. In this case, if the fibers are identical and periodically spaced,
2n-1 transmission wavelengths are required.

The diffraction grating 50 can be replaced or supplemented by a set of multi-dielectric filters, or by a set of phased array grating. A rung of Michelson, very effective for wavelengths of orders can also be used.

In addition, instead of fibers, one or more strips of lasers can be used as a means of referral input, and one or more photodetector arrays like output reception means.

A single strip of input and output fibers can also be employed.

In a particular embodiment of an n x n router, this includes a mirror and a diffraction grating, the mirror, the network and the fibers being fixed in a block of solid silica. A input fiber strip and output fiber strip parallels are placed in front of a photoetched slot on a plane reflection grating, perpendicular to grooves. A mirror concave is able to transform a divergent beam coming from any of the input fibers in a parallel bundle. The network is able to transform this beam by dispersing it angularly towards the concave mirror. This beam then has an image formed at one end of one of the output fibers in a position which depends on the wavelength. This configuration is aplanatic, afocal and has an amplification of 1. Thus, all angles from and towards fibers being identical, the best conditions are obtained with high coupling efficiency, the achromatism is perfect and the aberrations are practically zero when the mirror is parabolic.

For the calculation of specifications, the network is advantageously in a Littrow configuration. In addition, we preferentially use an OP (Out of Plane) configuration to avoid a direct return to an optical amplifier located short distance. In this configuration, the component uses a strip of fibers entering the home of the dispersive network device, so that no light can be coupled directly to the output fibers at a wavelength corresponding to a Littrow condition. The output fiber strip is arranged for this above that of the input fibers.

An 8 x 8 router referenced 1 according to the invention, shown in Figure 2, has eight inputs E1-E8 and eight outputs S1-S8. This 8 x 8 router is intended to transmit optical signals from any input E _i to any output S _i , in direction 5, the path of the optical signal being determined by its wavelength. Router 1 has two 4 x 4 routers referenced 30 and 40 respectively, which are 4 x 4 routers such as the one previously described (Figures 1A and 1B). Optionally, it can also be traditional 4 x 4 routers. The routers 30 and 40 each include four inputs 31-34 and 41-44 respectively, and four outputs 35-38 and 45-48. The outputs 35-38, 45-48 of routers 30 and 40 lead directly to outputs S1-S8 of router 1.

Router 1 also has four couplers achromatic in X referenced 10, 15, 20, 25 each having respectively two inputs 11, 12; 16, 17; 21, 22 and 26, 27, and two outputs 13, 14; 18, 19; 23, 24 and 28, 29. Entries 11, 12; 16, 17; 21, 22; 26, 27 of couplers 10, 15, 20, 25 in X correspond respectively to the inputs E1-E8 of router 1. Each of the couplers 10, 15, 20, 25 also has one of its outputs, respectively 13, 18, 23, 28, connected to one of the inputs, respectively 31, 32, 33, 34, of a first router 30, and its other output, respectively 14, 19, 24, 29, connected to one of the inputs, 41, 42, 43, 44, respectively, of the second router 40.

The respective transmission spectra 67 and 68 of the routers 30 and 40, represented in FIG. 3, are in the form of combs with teeth, respectively 71-73 and 74-76. The spectra 67 and 68 being plotted along axes 65 and 66, respectively of wavelengths λ and of transmission T, have their teeth 71-76 centered on the transmission wavelengths of routers 30 and 40. By taking up the correspondence matrix previously given, the teeth 71, 72 and 73 of the spectrum 67 are, for example, respectively centered on the wavelengths λ ₁ , λ ₂ , λ ₃ , the wavelengths λ _i being classified in ascending order . Similarly, the teeth 74, 75 and 76 of the spectrum 68 are centered on the wavelengths λ ' ₁ , λ' ₂ , λ ' ₃ .

In the embodiment, the teeth 71-76 have heights approximately identical and equal to H. Special features of the spectra 67 and 68 are constituted by the widths L of the teeth 71-76 at mid-height H / 2 and by the spacings D between the successive transmission wavelengths λ _i . As a first approximation, the widths L at mid-height are similar for all the teeth, as well as the spacings D. The ratio R = L / D is significant for the capacities of the routers 30 and 40. The larger this ratio, the more the processing capacities of routers 30 and 40 are high.

The routers 30 and 40 are chosen so that their transmission wavelengths λ _i and λ ' _i are interposed. So we have: λ ' 1 <λ 1 <λ ' 2 <λ 2 <λ ' 3 <λ 3

In operation, a signal at a given wavelength arrives at any one of the inputs E _i of the router 1, then at one of the couplers 10, 15, 20, 25. The signal is then transmitted to the two outputs of this coupler with in each an energy divided by two, the couplers being achromatic. The optical signal thus reaches an input from each of the routers 30, 40. Since the signal wavelength corresponds to a transmission wavelength of only one of the spectra 67, 68 of the routers 30, 40 , the signal is only transmitted in this router, to the appropriate output selected according to the wavelength. The targeted output S _j is thus reached by the signal.

Router 1 therefore has a global transmission spectrum which jointly admits teeth 71-76 of the two spectra 67 and 68 routers 30 and 40. At constant width at half height, equal to L, the spacing D between transmission wavelengths is thus significantly reduced, this reduction being able to go up to a factor 2. For a given available spectral band, the number of transmission wavelengths can therefore be multiplied by 2, and therefore also the number of users. The R report can itself be multiplied by 2, making selection easier of a transmission wavelength.

A second example of embodiment of an N x N router according to the invention is provided by a 12 x 12 wavelength router referenced 2, shown in Figure 4. This router has twelve inputs P1-P12 and twelve outputs P13-P24. It also includes four 3 x 3 wavelength routers referenced 130, 140, 150, 160, each having three entries 131-133, 141-143 respectively, 151-153, 161-163 and three outputs 134-136, 144-146, 154-156 and 164-166. The outputs of routers 130, 140, 150, 160 correspond respectively at outputs P13-P24 of router 2.

Router 2 also has three couplers 4 x 4 achromatic, referenced 80, 90 and 100. These couplers each have four entries, respectively 81-84, 91-94 and 101-104 and four outputs, respectively 85-88, 95-98 and 105-108. The inputs of couplers 80, 95, 100 correspond respectively to the inputs P1-P12 of router 2, and the four outputs of each of the couplers 80, 90, 100 are each connected to an input from one of the routers 130, 140, 150, 160.

Each of the couplers 80, 90, 100 is actually made up of from four couplers in X. So, as we can see on the Figure 5, the coupler 80 has four 2 x 2 couplers referenced 111-114 each comprising two inputs, respectively 81, 82; 83, 84; 125, 126; 127, 128 and two outputs, respectively 121, 122; 123, 124; 85, 86; 87, 88. Two of the X couplers, 111, 112, are arranged on a first level, their entries 81-84 being those of coupler 80. The other two couplers in X, 113 and 114, are arranged on a second level, their outputs 85-88 being those of the coupler 80. In addition, the outputs 121-124 of each of the two couplers 111, 112 of the first level are each connected to a input 125-128 of one of the couplers 113, 114 of the second level. The two other 4 x 4 couplers, 90 and 100, are made so similar.

Router 2 also includes 24 achromatic couplers in Referenced 120 there, each of them comprising a main arm 115 and two secondary arms 116 and 117. Each of the inputs P1-P12 and of outputs P13-P24 of router 2 is connected to the main arm 115 of one of the Y couplers 120. The 120 couplers are intended for serve as means of transmission, with two-way propagation, two branches 116, 117 of each of the couplers 120 being provided for opposite directions 118, 119 of signal propagation. The router 2 is thus intended for signal transmissions, both in one direction 3 from inputs P1-P12 to outputs P13-P24, and in an opposite direction 4.

The routers 130, 140, 150, 160 have transmission spectra 175, 180, 183, 186 having comb shapes comprising teeth, respectively 176-178; 181, 182; 184, 185; 187, 188, centered on wavelengths λ ₁ , λ ₂ , λ ₃ ; λ ' ₁ , λ'₂; λ '' ₁ , λ ''₂; λ ''' ₁ , λ''' ₂ .

The teeth of the four spectra 175, 180, 183, 186 of the routers 130, 140, 150, 160 are alternated, that is to say that we have: λ 1 <λ ' 1 <λ '' 1 <λ ''' 1 <λ 2 <λ ' 2 <λ " 2 <λ '" 2 <λ 3

In operation, a signal at a given wavelength reaches one of the inputs of one of the couplers 80, 90 or 100 and is transmitted to the four outputs of this 4 x 4 coupler with a reduction energy by a factor of 4. The optical signal is thus transmitted to a input of each of the four routers 130, 140, 150, 160. Being since the signal wavelength is only a wavelength transmission of only one of the spectra 175, 180, 183, 186 of 3 x 3 routers, signal transmission only takes place in this router, to the selected output according to the wavelength of the signal.

Router 2 therefore has a general transmission spectrum having the set of teeth 176-178, 181, 182, 184, 185, 187, 188 spectra 175, 180, 183, 186 of the four routers 130, 140, 150, 160. The width at mid-height of the teeth is thus preserved, and the inter-wavelength spacing of transmission substantially reduced, this reduction being able to reach a factor of 4. Furthermore, signals can come simultaneously from outputs P13-P24 to inputs P1-P12, according to the same principle. The same wavelength can thus be used in both directions of communication between two users, which doubles the router capabilities 2.

The energy losses of routers 1 and 2 are low, corresponding to factors of the order of 2 and 4 respectively. The presence of optical amplifiers in the switching compensates for the effects of these losses. It is however possible to make losses due to couplers negligible, in combination with couplers and selection means wavelengths. These means can be obtained, for example, by a two-wave interferometer, such as a Michelson which can be placed in an integrated optical plate. In this case, the optical signal leaving one of the couplers is not transmitted selectively only to the router having a wavelength of transmission corresponding to the wavelength of the signal.

Although the teeth of the combs of separate n x n routers have been shown dissociated, they can also overlap, the important thing being the centering of each of the teeth over a length given transmission wave. In the examples shown, we have shown spectra whose teeth of different routers are interleaved; However, any other means of obtaining recovery complementary to the spectrum may be suitable. In particular, the alternation of spectral components from one router to another can relate to bands and no longer teeth, each band comprising several teeth. This configuration is advantageous in particular if the spacing Inter-wavelength transmission is irregular, the teeth being grouped by packages.

We can see that the basic 4 x 4 and 3 x 3 routers respectively used in routers 1 and 2 can be themselves routers according to the invention.

This possibility is especially interesting in the presence of a higher number n of inputs and outputs, the invention can be applied in cascade on two or more levels.

An improved version of the routing process implemented with the router N x N of the invention can be implemented.

Considering, for example, router 1 previously described (Figure 2), it is desirable that several any of the inputs E1-E8 can communicate simultaneously with the same outputs S1-S8. In the basic version previously exposed, the transmission of signals from two inputs associated with a same 2 x 2 coupler, for example the inputs E1 and E2 and the coupler 10, and directed to the same output, for example S1, causes a interference between the two signals.

To remedy this, a first embodiment consists in sending, respectively at E1 and E2, signals having distinct wavelengths, but arranged on the same tooth of the transmission spectrum 67 of the router 30, as shown in the Figure 7. Thus, if tooth 71 of spectrum 67 corresponds to an optical path from input 31 of router 30 to output S1, the wavelength for E1 is equal to λ _1a and that for E2, λ _1b . The wavelengths λ _1a , λ _1b are arranged so as to produce on the tooth 71 preferably high amplitudes of transmission, that is to say close to the maximum value 70 reached approximately for the wavelength λ ₁ average, on which the tooth 71 is centered. The lengths λ _1a and λ _1b are therefore preferably close to λ ₁ . What is more, they are advantageously symmetrical with respect to λ ₁ , so that the corresponding transmission amplitudes are equal or close.

Thanks to this dissociation of the wavelengths of the signals sent in E1 and E2, the signals received simultaneously in S1 from E1 and E2 can be reconstructed by separation of the wavelengths λ _1a and λ _1b . This separation can, for example, be carried out by means of a coherent detection filter.

It is clear that the same mode of implementation is applicable to all of the inputs E1-E8 of router 1, by dissociation systematic of the two corresponding wavelengths respectively to the two inputs of each of the 2 x 2, 10, 15, 20, 25 couplers, and to one of teeth 71-76 from one of spectra 67, 68, according to output S1-S8 referred.

According to an embodiment of the routing method, for simultaneously send signals from E1 and E2 to S1, we choose respectively two wavelengths of distinct orders, allowing both signals to be routed from input 31 of router 30 to its exit 35.

In practice, high orders are necessary, which makes advantageous the presence of a Michelson echelon in router 30.

This method of implementation is, like the first, applicable to all of the inputs E1-E8, the two modes can be possibly combined. For example, one or the other can be used according to the spectrum teeth.

The routing method described, consisting of sending to the inputs of the same signal coupler with wavelengths separate, to transmit them simultaneously to the same output of the router N X N, is also valid for m greater than 2.

For example, in router 2 described above (Figure 4), signals from the four inputs P1-P4 can be sent simultaneously associated with coupler 80 to the same output P13 of router 2. For this do, the four signals corresponding respectively to the four P1-P4 inputs have separate wavelengths.

In the first embodiment, the four wavelengths are distributed in the tooth of the spectrum 175 associated with the transmission of a signal from the input 131 of the router 130 to its output 134, this tooth being, for example , that referenced 176. The four wavelengths are advantageously arranged close to λ ₁ , and symmetrically with respect to it.

In the second mode of implementation, they have orders distinct.

Of course, it is possible that only part of the four inputs P1-P4 receive signals simultaneously, towards the output P13.

The light sources connected to the P1-P12 inputs of router 2 and the detection means connected to the outputs P13-P24 are however preferably provided for respectively transmitting and detecting automatically signals at defined distinct wavelengths in the routing process chosen, which allows recognition signals in all cases.

The router of the invention can be implemented in a technology based on optical fibers or in integrated optics.

The router N x N of the invention can be the subject of an implementation partial work, only part of its N entries being used to receive optical signals. The number of N entries actually in service being equal to M, with M <N, the router N x N then behaves like an M x N router.

Example 1

In this first application example, the router according to the invention is a 40 x 40 router comprising two 20 x 20 routers and 20 achromatic couplers in X. Each of the 20 x 20 routers corresponds to a silica component, with a focal length of 119.512 mm, a network of 600 lines / mm, with a fiber holder with double strip of fibers spaced 42.54 µm apart. The first router is in collimation in the center of the field for 1548.5145 nm, and the second router has a spectrum shifted by half a period thanks to a stickers at 1548.5145 ± 0.4 nm. A double bar of 20 equally spaced fibers is disposed at the hearth.

The transmission wavelengths of the first router 20 x 20 range from 1533.2 nm to 1563.9 nm with inter-length spacing 0.8 nm transmission wave.

• pertes de 4 dB ± 1 dB;
• diaphotie intrinsèque < - 55 dB d'une voie à une autre ;
• perte retour < - 25 dB ;
• sensibilité de polarisation < 1 dB ;
• élargissement d'impulsion dû au réseau égal à 38,6 ps ;
• précision de voie de longueur d'onde : ± 0,05 nm.

The spectra of the 20 x 20 routers are such that the width at half height of the teeth, which have approximately a Gaussian shape, is 0.25 nm ± 0.02 nm. In addition, 20 x 20 routers have the following properties:

• losses of 4 dB ± 1 dB;
• intrinsic crosstalk <- 55 dB from one channel to another;
• return loss <- 25 dB;
• polarization sensitivity <1 dB;
• pulse widening due to the network equal to 38.6 ps;
• wavelength channel accuracy: ± 0.05 nm.

The spacing between transmission wavelengths (equal 0.8 nm) is chosen constant, which avoids additional losses up to 3 dB.

20 x 20 routers are compatible with data rates of 10 Gbit / second on each channel.

The 20 x 20 wavelength matrix of the first 20 X router 20 was calculated taking into account the exact silica index of each wavelength, by iterative adjustment to values of reference. The matrix obtained is shown in Figure 8; the 20 columns corresponding to the inputs, and the 20 rows to the outputs. The indicated values are expressed in nm. The default of adjustment remains less than 0.008 nm, which is negligible.

Example 2

An 80 x 80 router includes two 40 x 40 and 40 routers achromatic couplers in X.

• espacement inter-longueurs d'onde de transmission : 0,4 nm
• largeur à mi-hauteur des dents : 0,25 nm ± 0,03 nm
• pertes < 7 dB ± 2 dB ;
• diaphotie d'une voie à une autre < - 60 dB.

The 40 x 40 routers verify the following specifications:

• transmission wavelength spacing: 0.4 nm
• width at mid-height of the teeth: 0.25 nm ± 0.03 nm
• losses <7 dB ± 2 dB;
• crosstalk from one channel to another <- 60 dB.

These 40 x 40 routers are compatible with data rates of Gbit / second on each channel.

Example 3

A 6 x 6 router has two 3 x 3 routers made using 6 multiplexers each made in technology with shared optical function with focal length 119.512 mm, space between fibers 32 µm and network of 300 lines / mm.

The multiplexers of the first 3 x 3 router are associated with wavelengths 1552.517 nm, 1550.916 nm and 1549.315 nm. Those the second 3 x 3 router, at the same wavelengths offset by ± 0.8 nm.

The 6 x 6 router also has 3 X couplers made in fused fibers technique with close hearts (fused coupler).

Claims (15)

1. An N x N wavelength router (1, 2) comprising N inputs (E1-E8, P1-P12) and N outputs (S1-S8, P13-P24) provided to transmit optical signals each having a wavelength from the inputs to the outputs, the N x N router (1, 2) also comprising switching means capable of directing each of the optical signals from any one of the N inputs to any one of the N outputs according to the wavelength of said signal, the switching means comprising :

   n m x m couplers (10, 15, 20, 25, 80, 90, 100) each having m inputs (11, 12, 16, 17, 21, 22, 26, 27, 81-84, 91-94, 101-104) et m outputs (13, 14, 18, 19, 23, 24, 28, 29, 85-88, 95-98, 105-108), N being equal to n x m and the N inputs of the n m x m couplers (10, 15, 20, 25, 80, 90, 100) being the inputs (E1-E8, P1-P12) of the N x N router (1,2),

   m n x n routers (30, 40, 130, 140, 150, 160) each having n inputs (31-34, 41-44, 131-133, 141-143, 151-153, 161-163) and n outputs (35-38, 45-48, 134-136, 144-146, 154-156, 164-166), each of said n inputs being connected to one of the outputs of, respectively, the n m x m couplers (10, 15, 20, 25, 80, 90, 100) and the N outputs of the m n x n routers (30, 40, 130, 140, 150, 160) being the outputs (S1-S8, P13-P24) of the N x N router, each of the n x n routers being capable of switching an optical signal having a wavelength, from any one of its n inputs to any one of its n outputs, according to the wavelenght of said signal, said n x n router (30, 40, 130, 140, 150, 160) having a transmission spectrum (67, 68, 175, 180, 183, 186) according to the wavelength in the form of a series of peaks, characterized in that the series of peaks of the m n x n routers are different one another in order to allow a selection according to the wavelength for any one of said N inputs (E1-E8, P1-P12) of the N x N router (1, 2), both one of the m n x n routers and one of the n outputs of said n x n router.
2. An N x N router according to Claim 1, characterized in that the transmission spectrum (67, 68, 175, 180, 183, 186) of each of the m n x n routers (30, 40, 130, 140, 150, 160) comprising wavelength bands and each of said bands comprising series of peaks (71-76, 176-178, 181, 182, 184, 185, 187, 188), the transmission spectra of m n x n routers comprise intercalated bands.
3. An N x N router according to Claim 2, wherein the series of peaks (67, 68, 175, 180, 183, 186) of the m n x n routers (30, 40, 130, 140, 150, 160) have their peaks (71-76, 176-178, 181, 182, 184, 185, 187, 188) intercalated.
4. An N x N router according to any one of the previous claims characterized in that the series of peaks (67, 68, 175, 180, 183, 186) of the m n x n routers (30, 40, 130, 140, 150, 160) have peaks (71-76, 176-178, 181, 182, 184, 185, 187, 188) which are completely dissociated from peaks of others series of peaks.
5. An N x N router according to any one of the previous claims characterized in that each of the m x m couplers (10, 15, 20, 25, 80, 90, 100) is an achromatic coupler with uniform distribution of energy between the outputs thereof (13, 14, 18, 19, 23, 24, 28, 29, 85-88, 95-98, 105-108).
6. An N x N router according to any one of claims 1 to 4, characterized in that each of the m x m couplers (10, 15, 20, 25, 80, 90, 100) is a wavelength distribution coupler capable of transmitting the energy of an optical signal having a wavelength, only through the output of said in x m coupler connected to the n x n router (30, 40, 130, 140, 150, 160) whose series of peaks (67, 68, 175, 180, 183, 186) includes said wavelength.
7. An N x N router according to any one of the previous claims characterized in that the m x m couplers (10, 15, 20, 80, 90, 100) are made up of 2 x 2 couplers (10, 15, 20, 111-114), each having two inputs (11, 12, 16, 17, 21, 22, 26, 27, 81-84, 125-128) and two outputs (13, 14, 18, 19, 23, 24, 28, 29, 85-88, 121-124).
8. An N x N router according to Claim 7, characterized in that it comprises a first level of 2 x 2 couplers (111, 112) whose inputs (81-84) are the inputs (P1-P4) of the N x N router (2), and a final level of 2 x 2 couplers (113-114) whose outputs (85-88) are connected to the inputs (131, 141, 151, 161) of the n x n routers (130, 140, 150, 160), the inputs (125-128) of the 2 x 2 couplers (113, 114) which do not belong to said first level being connected to the outputs (121-124) of 2 x 2 couplers (111, 112) and the outputs (121-124) of the 2 x 2 couplers (111, 112) which do not belong to said final level being connected to the inputs (125-128) of 2 x 2 couplers (113, 114).
9. An N x N router according to any one of the previous claims characterized in that it comprises Y couplers (120) each having a main arm (115) and two secondary arms (116, 117), the inputs (P1-P12) and the outputs (P13-P24) of the N x N router (2) being connected to the main arms (115) of said Y couplers (120), said N x N router (2) allowing the sending of optical signals simultaneously from its inputs to its outputs and from its outputs to its inputs, said optical signals circulating in opposite directions (3, 4) in the two secondary arms (116, 117) of each of the Y couplers.
10. An N x N router according to any one of the previous claims characterized in that each of the n x n routers comprises :

    a transmission medium comprising a first row of n inputs and a second row of n outputs, the first and second rows being arranged in parallel and the transmission medium having a planar transmission surface,

    a diffracting element positioned opposite said transmission surface,

    a focusing lens positioned between the transmission medium and the diffracting element,

    the diffracting element and the focusing lens being capable of producing, from any one of the inputs, an image corresponding to any one of the outputs, according to the wavelength of said optical signals.
11. A method of optical routing carried out by means of an N x N router (1, 2) according to any one of the previous claims, wherein optical signals, each having a wavelength, are sent from the inputs (E1-E8, P1-P12) of the N x N router to its outputs (S1-S8, P13-P24) characterized in that to be able to send optical signals simultaneously from at least two of the m inputs (11, 12, 16, 17, 21, 22, 26, 27, 81-84, 91-94-101-104) of at least one of the n m x m couplers (10, 15, 20, 25, 80, 90, 100) in the direction of the same of N outputs (S1-S8, P13-P24) of the N x N router (1, 2) without risk of interference, said optical signals have wavelengths which are distinct one from another.
12. A method of optical routing according to Claim 11, characterized in that said output (S1-S8) of the N x N router (1) being one of n outputs (35-38, 45-48) from one of the m n x n routers (30, 40) and the series of peaks (67, 68) of said n x n router (30, 40) having peaks (71-76), the wavelengths of said optical signals are distributed within one of said peaks (71-76).
13. A method of optical routing according to Claim 11, characterized in that the wavelengths of said optical signals have distinct orders.
14. A communication network comprising at least one N x N router (1, 2) according to any one of claims 1 to 10.
15. A communication network comprising at least one N x N router (1, 2) implementing a routing method according to any one of claims 11 to 13.

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